Metallic solderability preservation coating on metal part of semiconductor package to prevent oxide

Abstract

Embodiments of the present invention are directed to metallic solderability preservation coating on connectors of semiconductor package to prevent oxide. Singulated semiconductor packages can have contaminants, such as oxides, on exposed metal areas of the connectors. Oxidation typically occurs on the exposed metal areas when the semiconductor packages are not stored in appropriate environments. Copper oxides prevent the connectors from soldering well. An anti-tarnish solution of the present invention is used to coat the connectors during sawing, after sawing, or both of a semiconductor array to preserve metallic solderability. The anti-tarnish solution is a metallic solution, which advantageously allows the semiconductor packages to not need be assembled immediately after fabrication.

What is claimed is: 
     
       1. A semiconductor package after singulation, the semiconductor package comprising:
 a metal strip having a plurality of connectors, the plurality of connectors having:
 multiple exposed surfaces after singulation, wherein the exposed surfaces of the plurality of connectors have a layer of anti-tarnish solution configured to allow the semiconductor package to need not be assembled immediately after singulation; and 
 non-exposed surfaces after singulation, wherein the non-exposed surfaces of the plurality of connectors are coated with a layer of lead finished material prior to singulation and with a layer of the anti-tarnish solution over the layer of lead finished material after singulation. 
 
 
     
     
       2. The semiconductor package of  claim 1 , wherein the anti-tarnish solution is a metallic solution. 
     
     
       3. The semiconductor package of  claim 1 , wherein the anti-tarnish solution is one of tin, silver, gold, and nickel-gold. 
     
     
       4. The semiconductor package of  claim 1 , wherein the anti-tarnish solution is configured to fill crevices in the exposed surfaces. 
     
     
       5. The semiconductor package of  claim 1 , wherein the anti-tarnish solution is configured to prevent metal oxidation. 
     
     
       6. The semiconductor package of  claim 1 , wherein the thickness of the layer is about 0.35 micron. 
     
     
       7. The semiconductor package of  claim 1 , wherein the thickness of the layer is about 1 micron. 
     
     
       8. The semiconductor package of  claim 2 , wherein the metallic solution is configured to protect the plurality of connectors from contamination. 
     
     
       9. The semiconductor package of  claim 1 , wherein the thickness of the layer of lead finished material is about 10 microns. 
     
     
       10. The semiconductor package of  claim 1  wherein the exposed surfaces after singulation are oriented to a side of the semiconductor package. 
     
     
       11. The semiconductor package of  claim 1  wherein the exposed surfaces after singulation are oriented to a mounting surface of the semiconductor package. 
     
     
       12. The semiconductor package of  claim 2 , wherein the metallic solution is a dense metal grain deposit with large and polygonized crystal structures. 
     
     
       13. The semiconductor package of  claim 2 , wherein the metallic solution is configured to preserve metallic solderability. 
     
     
       14. The semiconductor package of  claim 1 , wherein the plurality of connectors has a uniform topography on the surfaces of the plurality of connectors. 
     
     
       15. The semiconductor package of  claim 1 , wherein the surfaces of the plurality of connectors are wet surfaces to promote a homogeneous coating of the anti-tarnish solution.